The head of a leading British animal rights group has slammed the Aintree Grand National as "disgusting and shameful" after two more equine lives were lost on Saturday.

The British Horseracing Authority struck back, saying their evidence indicated that changes and improvements in safety made over the years had led to an overall decrease in injuries and fatalities at the National and in general.

Media commentators agreed it had been a black day for the sport after 28-1 outsider According To Pete and Cheltenham Gold Cup winner Synchronised (10-1) had to be put down after meeting grief at the famed Becher's Brook obstacle.

Their deaths, following two in 2011, brought the number of fatalities at the world famous Liverpool race since 1996 to 18 and angered Animal Aid director Andrew Tyler.

He told the website www.animalaid.org.uk: "The Grand National is a disgusting and shameful spectacle masquerading as sport. There is nothing sporting about an event that routinely kills so many horses.

"It is quite simply the worst kind of mob entertainment. For anyone who genuinely cares about horses watching this race was an utterly depressing and melancholy experience."

But the BHA's new chief executive Paul Bittar said the issue had to be judged over a period of time and the decade since 2000 had been the safest on record for the National with a fatality rate of 1.5 percent compared to 3.3 percent at the start of the 1990s.

His statement added: "In November last year, the BHA published the findings from a comprehensive and detailed review of all elements of the Grand National.

"At this stage, we believe it would be premature to suggest that modifications to the course and other changes have not been effective or will not yet prove to be effective.

"Since the review and the implementation of changes, four races have been held over the course without incident prior to yesterday's running of the Grand National."

Unique fences

Royal Society for the Protection of Animals (RSPCA) chief executive Gavin Grant, speaking to the BBC, described the 40-strong field as a "heck of a lot" and called for another look at Aintree's unique fences including Becher's with its famous drop on the landing side.

Becher's was among obstacles modified after the 2011 deaths but Grant said: "We need to look at the landing areas. Some improvements have been made there, but when you've got a drop on the other side of the fence a horse isn't expecting that."

Bittar said: "We are reasonably advanced in the process of examining the incidents which led to Synchronised and According To Pete being put down.

"While that process still needs to be completed, it is relevant to point out that although both horses lost their riders jumping Becher's Brook, Synchronised galloped away from the fence seemingly without injury and then subsequently incurred a fracture to a hind leg when jumping riderless, while According To Pete was brought down by another horse on the second circuit."

The deaths overshadowed an exciting victory by 33-1 chance Neptune Collonges, who won by a nose from Sunnyhillboy (16-1) in the closest finish in the race's long history.

The result was extra heartache for trainer Jonjo O'Neill and owner JP McManus who sent out both Sunnyhillboy and the ill-fated Synchronised, a Gold Cup hero 29 days previously.

Frank Berry, racing manager to McManus, said: "The horse looked perfect when he got up from the fall and he galloped away and jumped away afterwards.

"When he was up and running again you'd be hoping he'd be fine afterwards, they usually are, but what happened happened and it was very sad."

The outcome was a first National success for champion trainer Paul Nicholls and jockey Daryl Jacob. Neptune Collonges, a seasoned campaigner, has now been retired from the sport at the behest of owner John Hales who lost his famous chaser One Man in a fall at Aintree in 1998.